The present invention relates in general to ball valves, and in particular to a cut-off valve having locking means operatively connected to the ball element to prevent rotation, keeping the ball element in one or more preset operative conditions between the maximum open and closed condition of the valve.
Ball valves are commonly used to provide efficient and extremely reliable means to cut-off the flow of a fluid, which may operate quickly even at high pressures.
However, a problem arising in commonly used ball valves is the difficulty of "choking" that is to open or close partially the valve locking the closing or ball member in a preset working condition, avoiding accidental or intentional operations which can change the present operative condition of the valve. This disadvantage is particularly felt in those applications for which the passage of fluid must be maintained at a preset value, and accidental or deliberate manipulations of the valve, such as could alter or modify the operative conditions downstream which in certain working conditions might be undesirable or dangerous, must be prevented.